1. Field of the Invention
The present invention relates to a printing apparatus and a printing method that print an image on a print medium by using a plurality of arrays of nozzles, each capable of ejecting ink onto the print medium.
2. Description of the Related Art
Generally a print head used in an inkjet printing apparatus has arrayed therein a plurality of nozzles (printing elements), each comprising an ink ejection opening and a liquid path to supply ink to the opening. To allow for printing color images, a plurality of such print heads corresponding to different color inks are used.
A serial scan type inkjet printing apparatus prints an image on a print medium by alternating a printing scan, that ejects ink from the ejection openings as the print head travels in a main scan direction, and a conveying operation that conveys the print medium in a sub-scan direction crossing the main scan direction. The print head is formed with a nozzle array (printing element array) having a plurality of nozzles arrayed in the sub-scan direction. For faster printing speed, a bidirectional printing method is employed, in which the printing scan is executed both when the print head is moved in one of two opposite directions (forward scan) along the main scan direction and when it is moved in the other direction (backward scan).
In an inkjet printing apparatus that prints an image by using a plurality of nozzle arrays formed in one or more print heads, image degradations may occur when print positions deviate among nozzle arrays. For example, in printing a pattern of vertical blue lines extending in the sub-scan direction, lines printed by a cyan ink nozzle array and lines printed by a magenta ink nozzle array must be aligned to overlap each other. If the print positions of these lines are shifted in the main scan direction, the lines fail to align with each other, making it impossible to print a pattern of high-quality vertical blue lines.
If image impairments are caused by such print position deviations, an adjustment needs to be made to align the print positions in the main scan direction among a plurality of nozzle arrays (also referred to as a “misregistration adjustment”).
As one method for such a misregistration adjustment, Japanese Patent Laid-Open No. 2007-015261 discloses a method that determines inclinations of the nozzle arrays (inclinations of print heads) and misregistration adjustment values among a plurality of nozzle arrays.
However, when a plurality of printing modes are used, the print positions may not be able to be adjusted properly among a plurality of nozzle arrays depending on the printing mode. For example, in a printing mode that uses all nozzles of a nozzle array to print an image and in a printing mode that uses a part of the nozzles of the nozzle array, the effect that the inclination of the nozzle array has on the print position deviation differs. Even if the print position adjustment value among a plurality of nozzle arrays is determined after the nozzle array inclination adjustment value has been determined, as in Japanese Patent Laid-Open No. 2007-015261, there may remain a small difference in the inclination adjustment of a magnitude less than the adjustment resolution between the nozzle arrays. Even a slight difference in the nozzle array inclination may produce different effects on the print position deviations in different printing modes. This means that the use of a single misregistration adjustment value, which is determined considering the inclinations of nozzle arrays as described above, may not be able to properly adjust the print positions of nozzle arrays for different printing modes.